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Topic: Lantern pinion interference question (Read 9131 times)

I've created two sets of wheels and lantern pinions. The first set is 64/8 and the second is 60/8. The 64 tooth minute wheel drives the 8 tooth pinion connected to the 60 tooth intermediate wheel (is this the "third wheel"?) which similarly drives the escapement wheel.

Both sets of gears are constucted in an identical manner (or so I think). The pitch diameters are proportional to the number of teeth, the depthing is proportionally the same, and the size and shape of the teeth (both wheel and pinion) are proportionally the same. I have used a slightly long wheel tooth as recommended for lantern pinions.

The problem I'm having is that while the first set of gears meshes smoothly, the second set does not. The pointed tips of the wheel teeth will occasionally collide with or chip against the pinions as they engage. This seems to occur when the escapement wheel is allowed to freewheel or when there is "slack" in the train (would this be termed gear "lash"?). It seems to happen when the escapement wheel has advanced too far so that the previous or "active" tooth is not bearing on a pinion tooth.

When I retard or resist the movement of the escapement wheel, the slack is taken out of the train and this collision does not occur; however, I'm concerned because I don't ever get the same effect with the first gear set. I'm thinking that this may be a symptom of either incorrect depthing or some other error that I've not yet discovered.

Check to see the axles are centered in wheel and pinion. Mount the axle in a drill press and slowly rotate it. Any sideways wobble will indicate your depthing isn't consistent around the circle.

According to Goodrich, "The Modern Clock," wheels driving lantern pinions have a more rounded addendum because the epicycloid for the wheel tooth is based on the pitch diameter of the pinion. (On regular pinions this is based on half the radius of the pinion.) He also suggests that for an eight pin lantern pinion the pins should be three units wide with the spaces between the teeth five units wide.